Ryan, the House Budget Committee chairman and author of a controversial proposal to privatize Medicare, has made it clear in recent days that he believes he can wield more influence from his position in the House.

As we have noted, potential Democratic candidates include former U.S. Sen. Russ Feingold, who lost his 2010 re-election bid in last year's Republican wave, Milwaukee Mayor Tom Barrett, and U.S. Reps. Tammy Baldwin and Ron Kind.